The present invention relates generally to the field of marking rubber articles, and in particular to a new and useful laser-assisted method of cutting a selected pattern into a multi-layered workpiece, unit or patch, and to the resulting product itself.
Tires are a source of high operating costs for most common carriers regardless of what they are shipping or carrying. A system is needed for tracking tire maintenance and predicting the life of a tire, as a preventative step for avoiding tire failures and reducing emergency roadside repair. Therefore, a system is needed for properly maintaining and managing tires, in particular commercially used tires, from the time a tire is born to the time that its usefulness ends. To this end, each tire must be provided with a unique and permanent identification mark that will always be accurately recognizable regardless of the normal wear and tear of the tire.
Several methods for marking rubber are known in the art, but do not have the permanence and accuracy that is needed for adequately managing and tracking a tire. For example, it is known in the art of marking rubber that a CO2 laser can be used to cut a rubber work piece. An important area of industrial application for CO2 lasers has been in cutting, marking, engraving, etching, trimming and perforating rubber items.
U.S. Pat. No. 5,478,426 to Wiler et al. discloses a method for ablating elastomeric materials with a laser to produce a pattern or design within the elastomeric material. The Wiler et al. patent requires an elastomeric multilayered work piece, having a first outer layer with a higher ablation rate than a second inner layer. As a result, the inner layer has a lower response to the laser, and any inadvertent impingement of the laser on the inner layer will not disturb or damage the inner layer. On the other hand, the multi-layered workpiece, unit or patch of the present invention preferably has an outer layer with a lower ablation rate than the inner layer or a substantially similar ablation rate to the inner layer.
The Wiler et al. patent also teaches the use of two different types of lasers (e.g., a YAG and a CO2 laser) to cut different layers, but does not teach the use of a single full-powered CO2 laser set to reduced power output to cut a single layer of rubber. There are significant differences between a YAG and CO2 laser, including wavelength of the emitted light, beam shape, beam delivery, and power. In particular, a YAG laser is a solid state laser emitting a light at a wavelength of 1.06 microns near infrared while a CO2 gas laser emits a light at a wavelength of 10.6 microns or mid-IR. A CO2 laser is therefore absorbed differently by rubber than a YAG laser.
The Wiler et al. patent also does not teach cleaning the area of the cut pattern with a cleansing fluid.
U.S. Pat. No. 5,880,430 to Wein discloses a method and apparatus for laser etching a design into a workpiece with the assistance of a computer. The computer may be used to select the operation parameters for the laser such as laser beam intensity and the desired pattern or design.
In one embodiment of the Wein patent, a first material base, that is not easily engravable by a laser, lies beneath a second material that is easily engravable with a laser. The laser etches the preselected design into the second material until it reaches the interface between the two materials. Multiple color or multiple layer designs may be formed from the removal of different portions of a layer. Although the patent discloses rubber as one type of material that is suitable for this process, the first layer must be a different material from the second layer. The Wein patent also does not teach a full powered CO2 laser operating at reduced power or a cleaning agent.
Also see U.S. Pat. No. 2,985,216 to Williams et al. and U.S. Pat. No. 5,061,341 to Kildal et al.
The prior art does not provide a method for marking a multi-layered and multi-colored rubber patch with a full powered CO2 laser that is operated at less than its full power capability and scans the rubber unit with a preselected pattern or design before ablating an outer layer to reveal inner layer portions of contrasting color. Furthermore, the prior art does not teach marking of a multi-layered rubber unit that comprises layers of the same type of material (e.g., rubber), but has an outer layer with a lower ablation rate (i.e. is more difficult to ablate) than the inner layer for ensuring durability and wear and tear protection for the resulting pattern for maintaining accuracy and recognition. Finally, the prior art does not teach the use of a cleaning agent containing a surface active agent and a solvent such as alcohol, for removing rubber residue from the unit.
It is an object of the present invention to provide a method for manufacturing a weather and wear resistant rubber identification unit for a tire with a selected pattern on the unit, and an identification unit made by that method.
The unit can be used as part of a tire tracking, inventory and use system. To this end the unit must be economical to make and extremely resistant to wear and weathering, while being marked with individual, unique and serialized patterns, such as a bar code. This is particularly true where the system is used for truck tires.
Accordingly, another object of the invention is to provide a multi-layered rubber identification or ID unit having an outer layer of one color and at least one inner layer of a contrasting color, scanning the outer layer of the unit with a laser beam from a high powered CO2 laser operated at less than full power output, to ablate the outer layer in the form of the selected pattern, to expose the at least one inner layer of contrasting color, the ablating step forming loose particles and residue particles, removing the loose particles from the unit using a vacuum and applying a cleaning fluid to the ID unit remove the residue particles from the unit.
The invention also includes using a cleaning fluid that contains solvent, such as alcohol and a surface active agent for reducing a tendency of the alcohol to evaporate, the method including rinsing the cleaning fluid from the unit and then drying the unit.
The alcohol is of the type know for use as a propellant and the surface active agent is a soap in the preferred form of the invention. Commercially available products know by the trademarks xe2x80x9cSpray n"" Washxe2x80x9d and xe2x80x9cScrubbing Bubblesxe2x80x9d both in aerosol form, have been found to be good cleaning agents.
The preferred form of the laser is a commercially available 100 Watt CO2 it was found that operating the laser at less than full power, e.g. at 30-40% less than full power, specifically at 60 watts or 60% power, ablated the outer ID unit layer more fully and evenly than a 60 watt laser of similar type. This also allows the laser beam to be scanned over the ID unit in one pass and quickly, to make the pattern quickly.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.